It’s either trivial or harder than it looks – (at least) four stalled projects named apns4j:
http://sourceforge.net/projects/apns4j/ (zero files in svn)
https://apns4j.dev.java.net/source/browse/apns4j/ (zero *.java in svn, same ownername as above)
http://code.google.com/p/apns4j/ (zero files in svn, same ownername as above)
http://github.com/netmask/apns4j (three commits)
I didn’t look closer – maybe the last was gifted with a mature birth. The first three …